Moreno’s Law: The US wants citizens to choose one passport — but the world moved on from bans on dual citizenship

In December 2025, US Senator from Ohio Bernie Moreno introduced a bill that would ban Americans from holding dual citizenship. The measure, dubbed the Exclusive Citizenship Act of 2025, would require people with two citizenships to choose one within a year or risk losing their US passport.

According to GovTrack estimates, the bill’s odds of passage are around 3%. But the point isn’t congressional probability. The real issue is how sharply the proposal clashes with the global trend of the past several decades.

Today, three out of four countries allow a person to obtain a second citizenship without losing the first. This comes from the MACIMIDE Global Expatriate Dual Citizenship Dataset, a database from Maastricht University covering 200 countries over the 1960–2020 period.

It’s important to clarify the limitation: MACIMIDE records only one side of the question—whether a state strips citizenship from its subjects if they voluntarily naturalize abroad. At the same time, the dataset does not show whether countries require immigrants to renounce their prior citizenship upon naturalization.

For anyone considering a second passport, however, the key question is usually different: will the country where the person already holds citizenship allow them to keep it?

That answer largely determines how workable residence and citizenship by investment (RCBI) programs are—when status is granted through investment or long-term residence. In effect, Moreno’s bill would place the United States among a small group of countries going against the broader liberalization trend.

The proposal also conflicts with the US Supreme Court’s line of cases stemming from Afroyim v. Rusk (1967). In addition, the US federal government does not keep reliable records of who actually holds dual citizenship; estimates range from 500,000 to 5.7 million Americans. And in some projections, eligibility for a second citizenship by origin could affect over 40 million people. In practice, that makes enforcement extremely difficult.

For the RCBI market, global acceptance of dual citizenship is a crucial factor. To understand why Moreno’s bill looks like an “outlier,” it helps to see how the world reached today’s state of affairs.

It started with bans by analogy with “dual marriage”

For much of the twentieth century, dual citizenship was often lumped together—both in legal and public debates—with tax evasion or draft evasion. In legal publications of the time, comparisons to “bigamy” appeared fairly often, and not always purely metaphorically.

International treaties from the 1930s to the 1960s treated overlapping citizenships as a problem to be eliminated rather than a right to be protected.

Then the consensus began to crack. In Europe, the 1963 Convention on the Reduction of Cases of Multiple Nationality assumed that states should strip citizenship from those who acquire another. But in the 1970s and 1980s, many countries started to withdraw from those provisions.

By 1997, the European Convention on Nationality had effectively shifted the approach: it became neutral about the fact of multiple citizenship itself—treating it as an undesirable phenomenon rather than an automatic violation.

A study by Vink et al. (2019) describes 75 policy changes under MACIMIDE’s binary logic. Of these, 85% were liberalizations, with the peak occurring in the 1990s–2000s.

The overall path looked roughly like this:

• 1960: about 38% of countries allowed dual citizenship
• 1990: about 50% (trend estimate using MACIMIDE)
• 2000: roughly 60% after reforms in Latin America and post–Cold War Europe
• 2017: about 73% according to Vink et al.
• 2020: 76% in the latest MACIMIDE update

What had been built for decades as the “norm” took about 30 years to dismantle.

Why it became possible: four factors

Gender equality in citizenship laws

This factor is often underestimated. Once countries began allowing mothers to pass citizenship to their children, the number of people effectively born with two citizenships increased automatically. As a result, stripping citizenship from those who didn’t make any “choice,” but simply were born under the right conditions, became increasingly controversial—both legally and morally.

Diaspora policy

In the 1990s and 2000s, a number of states implemented reforms quickly—for example, Colombia (1991), Dominican Republic (1994), Costa Rica and Ecuador (1995), Brazil (1996), and Mexico (1998). The logic was broadly similar: diasporas abroad actively lobbied for change.

Under older rules, emigrants had to choose between “belonging to the homeland’s politics” and normal integration where they lived. Diasporas demanded both.

Regional “contagion” of practices

Vink et al. showed that liberalizations happen significantly more often when neighboring countries have already taken steps in the same direction. It appears the “neighbors’ effect” works not only in business, but also at the level of states.

The end of the Cold War

When military conflicts between states were a common reality, dual citizenship could indeed raise questions about loyalty on the battlefield. As that fear weakened, the strongest argument for restrictions faded away too.

Who held out longer—and who “changed lanes”

Most countries have already adopted dual citizenship. The fastest movement occurred in the Americas and Oceania, while most EU countries do not impose restrictions.

Caribbean jurisdictions are especially telling, where citizenship-by-investment programs exist: all five such destinations recognize dual citizenship; otherwise, CBI schemes would be nearly unworkable. People typically don’t look for a second passport “just to give up the first.”

Recent changes also reflect the broader drift. Germany’s reform in June 2024 was among the most significant: the requirement to renounce the prior citizenship upon naturalization was abolished, and the residence period was reduced from eight to five years. After that, naturalization rates hit record levels.

In May 2025, South Africa’s Constitutional Court ruled that automatic loss of citizenship is unconstitutional—applying retroactively back to 1995. The “liberal” list also included Nigeria, Liberia (2022), and Malawi (2019).

At the same time, the group of “holdouts” may be shrinking, but it remains noticeable. Formally, China bans dual citizenship, yet in practice it is applied selectively. For the RCBI market, that matters: demand for second passports among Chinese citizens is consistently among the highest in the world.

Japan formally requires choosing one citizenship by age 22, but enforcement is uneven. In Singapore, Malaysia, and Indonesia, dual citizenship is also not recognized, making Southeast Asia one of the most restrictive regions globally. Austria allows dual citizenship only in situations that arise “not by the person’s will.” And the GCC (Gulf Cooperation Council) states formally prohibit dual citizenship.

Summaries of country status on this issue are often presented as catalogs, such as the IMI Citizenship Catalog.

Political and geopolitical impact

Sometimes restrictions return not from principle, but from calculations. In the MACIMIDE dataset, one sharp reversal stands out: Slovakia’s restriction in 2010.

The move came amid a similar step by Hungary: during the same period, Hungary was making naturalization easier for ethnic Hungarians living abroad. Slovakia—where around 500,000 ethnic Hungarians live—set a rule that a citizen who voluntarily acquires another citizenship loses Slovak citizenship.

This was straightforward geopolitics. Later, in 2022, some restrictions were softened, but the core of the ban remained.

Fewer exceptions and more “islands”: why the trend won’t stop

Citizenship-by-investment programs exist because people want to add citizenship, not replace one with another. That’s why global acceptance of dual citizenship is the foundation of the entire model.

And the effect is mutual. The more instances where an RCBI program grants status to someone who has never lived in the country—without catastrophic consequences—the weaker the arguments against liberalization become.

By normalizing multiple citizenship at scale, the programs themselves become part of the mechanism that sustains the overall policy shift.

As a result, the “holdouts” become fewer, and their positions become more isolated. For a market built on layering passports, that’s a key structural fact.

Moreno’s bill won’t reverse the global liberalization that has been forming for decades. Restrictive countries will remain exceptions, and the trajectory is, overall, fairly clear.

Data are based on the MACIMIDE Global Expatriate Dual Citizenship Dataset (Vink, De Groot, and Luk, 2015; V5, 2020) via Harvard Dataverse, and on Vink et al., “The International Diffusion of Expatriate Dual Citizenship,” Migration Studies 7, no. 3 (2019): 362–383. MACIMIDE tracks expatriate dual-citizenship policy and does not measure the destination country’s requirements to renounce prior citizenship upon naturalization.

If you’re considering a second passport or investment-based residence permit to broaden your mobility options, it’s crucial to understand the rules on dual citizenship and legal status in the target countries. The Moreno bill is a reminder that the world is moving away from strict bans, while residence and citizenship by investment (RCBI) programs are becoming increasingly relevant. Want to assess options tailored to your case (investment requirements, timelines, and document-related risks)? Reach out to Digital Nomad — we’ll help you navigate the current requirements and choose the most practical route.

Our Telegram channel about various types of Greek residence permits, digital nomad programs, and the Greek Golden Visa: @digitalnomadgr